4,363 research outputs found
Discovery of Extremely Large-Amplitude Quasi-Periodic Photometric Variability in WC9-Type Wolf-Rayet Binary, WR 104
We discovered that the Wolf-Rayet (WR)+OB star binary, WR 104, renowned for
its associated "dusty pinwheel nebula" recently spatially resolved with
infrared interferometry, exhibits strong quasi-periodic optical variations with
a full amplitude of 2.7 mag. Such a large-amplitude, continuous variation has
been unprecedented in a WR star. The optical quasi-period (~241 d) is in almost
perfect agreement with the interferometric period (243.5+/-3 d). The remarkable
agreement of the dominant period in optical variability with the orbital period
supports that the strongly varying dust obscuration is physically related to
the binary motion, rather than sporadic dust-forming episodes. Considering the
low orbital inclination (11+/-7 deg) and the nearly circular orbit inferred
from the interferometric observations, the strongly variable line-of-sight
extinction suggests that the highly structured extinction can be being formed
via an ejection of dust in the direction of the binary rotation axis. Another
viable explanation is that the three-dimensional structure of the shock front,
itself is the obscuring body. Depending on the geometry, the dusty shock front
near the conjunction phase of the binary can completely obscure the inner
WR-star wind and the OB star, which can explain the amplitude of optical fading
and the past observation of remarkable spectral variation.Comment: 5 pages, 4 figures, to appear in PASJ (Letters), using an alternative
style fil
Deep Transient Optical Fading in the WC9 Star WR 106
We discovered that the WR9-type star WR 106 (HDE 313643) underwent a deep
episodic fading in 2000. The depth of the fading (dV ~ 2.9 mag) surpassed those
of all known similar "eclipse-like" fadings in WR stars. This fading episode
was likely to be produced by a line-of-sight episodic dust formation rather
than a periodic enhancement of dust production in the WR-star wind during the
passage of the companion star though an elliptical orbit. The overall 2000
episode was composed of at least two distinct fadings. These individual fadings
seem to more support that the initial dust formation triggered a second dust
formation, or that the two independent dust formations occurred by the same
triggering mechanism rather than a stepwise dust formation. We also discuss on
phenomenological similarity of the present fading with the double fading of R
CrB observed in 1999-2000.Comment: 3 pages, 4 figures, to appear in Astron. Astrophys. (Letters
The Effects of Adherence to Asian Values and Extraversion on Cardiovascular Reactivity: A Comparison Between Asian and European Americans
This study investigated the effects of personality type and ethnicity on reactivity to stressful stimuli by examining acculturation and adherence to Asian American cultural values as moderators. Twenty-two Asian American and twenty-two European American students performed a mental arithmetic task and a speech task while cardiovascular (CV) reactivity was monitored. Level of extraversion, acculturation, and adherence to Asian American values were assessed. As predicted, Asian Americans exhibited less CV reactivity to stressful stimuli and lower levels of extraversion than European Americans. Support was found for adherence to Asian American values as a moderator of the relationship between level of extraversion and CV reactivity to stressful stimuli. The results illustrate that being connected to Asian American culture has protective value for less extraverted individuals, as adherence to Asian American values predicted less CV reactivity to stress. These findings shed light on how culture influences the form and function of personality and can influence physiological reactivity to stress. To the best of my knowledge, no research has investigated whether personality type has an effect on stress responses in Asian Americans and examined the differences in responses based on cultural adherence
Protective Effects of Radon Inhalation on Carrageenan-Induced Inflammatory Paw Edema in Mice
We assessed whether radon inhalation inhibited carrageenan-induced inflammation in mice. Carrageenan (1% v/v) was injected subcutaneously into paws of mice that had or had not inhaled approximately 2,000 Bq/m3 of radon for 24 h. Radon inhalation significantly increased superoxide dismutase (SOD) and catalase activities and significantly decreased lipid peroxide levels in mouse paws, indicating that radon inhalation activates antioxidative functions. Carrageenan administration induced paw edema and significantly increased tumor necrosis factor-alpha (TNF-α) and nitric oxide in serum. However, radon inhalation significantly reduced carrageenan-induced paw edema. Serum TNF-α levels were lower in the radon-treated mice than in sham-treated mice. In addition, SOD and catalase activities in paws were significantly higher in the radon-treated mice than in the sham-treated mice. These findings indicated that radon inhalation had anti-inflammatory effects and inhibited carrageenan-induced inflammatory paw edema
Five-Year Optical and Near Infrared Observations of the Extremely Slow Nova V1280 Scorpii
We present optical (, , , and ) and near
infrared (, and ) photometric and spectroscopic observations
of a classical nova V1280 Scorpii for five years from 2007 to 2011. Our
photometric observations show a declining event in optical bands shortly after
the maximum light which continues 250 days. The event is most probably
caused by a dust formation. The event is accompanied by a short ( 30
days) re-brightening episode ( 2.5 mag in ), which suggests a
re-ignition of the surface nuclear burning. After 2008, the band
observations show a very long plateau at around = 10.5 for more than 1000
days until April 2011 ( 1500 days after the maximum light). The nova had
taken a very long time ( 50 months) before entering the nebular phase
(clear detection of both [\ion{O}{iii}] 4959 and 5007) and is still continuing
to generate the wind caused by H-burning. The finding suggests that V1280 Sco
is going through the historically slowest evolution. The interval from the
maximum light (2007 February 16) to the beginning of the nebular phase is
longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10
months), or HR Del (8 months). It suggests that the mass of a white dwarf in
the V1280 Sco system might be 0.6 M_\mathrm{\sun} or smaller. The distance,
based on our measurements of the expansion velocity combined with the directly
measured size of the dust shell, is estimated to be 1.1 0.5 kpc.Comment: 17 pages, 14 figures, accepted for publication in A&
Earliest detection of the optical afterglow of GRB 030329 and its variability
We report the earliest detection of an extremely bright optical afterglow of
the gamma-ray burst (GRB) 030329 using a 30cm-telescope at Tokyo Institute of
Technology (Tokyo, JAPAN). Our observation started 67 minutes after the burst,
and continued for succeeding two nights until the afterglow faded below the
sensitivity limit of the telescope (approximately 18 mag). Combining our data
with those reported in GCN Circulars, we find that the early afterglow light
curve of the first half day is described by a broken power-law (t^{- alpha})
function with indices alpha_{1} = 0.88 +/- 0.01 (0.047 < t < t_{b1} days),
alpha_{2} = 1.18 +/- 0.01 (t_{b1} < t < t_{b2} days), and alpha_{3} = 1.81 +/-
0.04 (t_{b2} < t < 1.2 days), where t_{b1} ~ 0.26 days and t_{b2} ~ 0.54 days,
respectively. The change of the power-law index at the first break at t ~ 0.26
days is consistent with that expected from a ``cooling-break'' when the cooling
frequency crossed the optical band. If the interpretation is correct, the decay
index before the cooling-break implies a uniform ISM environment.Comment: 13 pages, 1 table and 2 figures. Accepted to the Astrophysical
Journal Letter
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